In a move timed for this week's Intergovernmental Panel on Climate Change meeting in Washington, D.C., several groups have issued reports addressing the potential environmental effects of a global warming and the need for governments to act as soon as possible to limit the pollutants responsible.

Late last month, the Environmental Protection Agency released a report to Congress on potential U.S. effects of global climate change, based on a range of conditions suggested by three major general-circulation climate models. The study's authors found that forests unable to cope with a warmer climate could begin dying back in 30 to 80 years, eventually moving the southern boundary of U.S. woodlands northward by about 400 miles. Even if these woodlands were to "migrate" northward at 60 miles per century--twice their fastest known rate--it's likely that the advance of their southern boundary would greatly outpace the forests' northern migration. A net loss of timberlands and the animal species inhabiting them could result, according to the report.

The EPA study also found that sea-level rise will probably outpace the ability of coastal marshes and swamps to migrate inland. A rise of just 1 meter -- in the middle range of the predicted 0.5 to 2 meters -- would likely result in a 26 to 66 percent loss of wetlands, the authors contend, "even if wetland migration were not blocked" by bulkheads, levees and other feats of human engineering. By 2055, annual U.S. demand for electricity might increase 4 to 6 percent above rates necessary without a global warming -- at an estimated additional cost of $33 billion to $73 billion annually. The EPA report also asserts that air pollution--especially smog ozone--can be expected to increase dramatically.

Though the total cost of adapting to these changes will undoubtedly be high, the authors conclude that those costs should be "affordable" for industrial nations. And while crop yields could drop severely--at least on a temporary basis--the EPA analysis suggests they should "be adequate to meet domestic needs" even under the more extreme scenarios.

Last week, the Paris-based International Energy Agency (IEA) issued a 230-page report identifying economic and technological options for reducing emissions of the pollutants driving a threatened climate change. One of the easiest near-term targets, IEA suggests, would be to switch from conventional coal- and oil-fired electrical generating plants to nuclear and "clean" fuels, including some additional use of natural gas. Other measures for reducing emissions of carbon dioxide include heavy taxes on fossil-fuel use.

Rectifying inefficiencies in motor vehicles could also offer near-term gains. But the report notes that trends toward larger cars, more driving and increased road congestion have offset many recent gains in automobile efficiency. A recent study offers a striking illustration of this point. According to the South Coast Air Quality Management District in El Monte, Calif., vehicles idling in traffic burn one-quarter of all fuel sold in Los angeles, Orange, Riverside and San Bernardino counties.

All options listed in the IEA report "imply radical changes at heavy cost, whether combined or considered separately," acknowledges IEA Deputy Executive Director John P. Ferriter. However, he says, "governments would be well advised to make an immediate start and build up their efforts [to stabilize carbon emissions] gradually."

A number of prominent U.S. scientists agree. Last week, the Union of Concerned Scientists sent President Bush an appeal--endorsed by 49 Nobel laureates and 700 members of the National Academy of Sciences -- that argues: "Only by taking action now [to mitigate global warming] can we insure that future generations will not be put at risk."

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